1. Field of the Invention
The present invention relates to a nitride semiconductor light emitting device and a method of manufacturing the same.
2. Description of the Related Art
A GaN nitride semiconductor is one of nitride semiconductors according to a related art. The GaN nitride semiconductor has been applied to an optical device such as a green or blue light emitting diode (LED) and high-speed switching and high-power electronic devices such as a metal semiconductor field effect transistor (MESFET) and a high electron mobility transistor (HEMT).
Particularly, in a light emitting device such as an LED and a semiconductor laser diode, a nitride semiconductor that has a p-type conductivity and emits blue light by disposing a group □ element such as Mg, Zn, or the like in a position of Ga, which is a group □ element of a GaN nitride semiconductor, is in the limelight.
FIG. 1A is a sectional view of a nitride semiconductor light emitting device according to a related art.
Referring to FIG. 1A, a light emitting device having a multiple quantum well (MQW) structure, which is one of GaN nitride semiconductors according to the related art, is grown on a substrate 1 generally formed of sapphire. A polycrystalline thin layer is grown into a buffer layer 2 on the substrate 1 at low temperature, and then a GaN underlayer 3 is stacked on the buffer layer 2 at high temperature. An active layer 4 for light emission is disposed on the GaN underlayer 3, and an AlGaN electric barrier layer 5 doped with Mg, an InGaN layer 6 doped with Mg, and a GaN layer 7 doped with Mg, which switch to p-type by a thermal annealing process, are sequentially stacked on the active layer 4.
An insulating layer 8 is formed on the GaN layer 7 doped with Mg and the GaN underlayer 3, and a p-type electrode 9 and an n-type electrode 10 are formed thereon, which forms a light emitting device.
FIG. 1B is a view illustrating light emitting of a nitride semiconductor light emitting device according to a related art.
Referring to FIG. 1B, the light emitted from the active layer 4 moves along light paths □, □ and □.
When light is incident from a material with an optically large refractive index to a material with a small refractive index, if an incident angle is greater than a predetermined angle (critical angle), the light is totally reflected on the interface. The light path □ is caused by such a total reflection.
Therefore, the light moving along the light path □ decreases a light emitting efficiency of the light emitting device including the active layer 4.
Also, in the related art, when the nitride semiconductor is etched to form the n-type electrode, then-type nitride semiconductor is etched using dry etching. This dry etching damages the nitride semiconductor, decreasing an optical characteristic and a current-voltage characteristic of the nitride semiconductor.